Digital edition

CERN Courier

Oct 4, 2006

Axion signature may be QED

Earlier this year the PVLAS collaboration announced the possible signature of the hypothesized particle known as the axion, in an experiment to measure light polarization rotation in a magnetic field (see CERN Courier June 2006 p11 and see CERN Courier July/August 2006 p19). Now a team of researchers in Lisbon has argued that what might have been detected is not an axion, but a new effect in quantum electrodynamics (QED).

Tito Mendonça, Dias de Deus and Castelo Ferreira of the Instituto Superior Técnico in Lisbon have argued that a beam of light propagating in a slowly rotating magnetic field can give rise to an infinite tower of frequency shifts proportional to the rotation frequency. The data from PVLAS may reflect a first measurement of this effect in pure QED, rather than evidence for an axion.